Johannes Kepler confirms his third law of planetary motion

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15 May, 1618

After rechecking his calculations, Johannes Kepler, confirms his third law of planetary motion on the 15th of May 1618.

Often referred to as the harmonic law because Kepler had the view of “music of the spheres”, the third law of planetary motion states that the square of the periodic times are proportional to the cubes of the mean distances from the sun.

The first law stated that all planetary orbits are elliptical with the sun lying at one of the foci. The second states that the line joining the planet and the sun sweeps equal areas in equal intervals of time.

Johannes Kepler was a German mathematician, astronomer, and astrologer who played a key role in the scientific revolution (there is no pun here) of the 17th century.